Mitsubishi Electric FR-E700EX Instruction Manual page 28

(2) Earthing (Grounding) precautions
 Always earth (ground) the motor and drive unit.
1) Purpose of earthing (grounding)
Generally, an electrical apparatus has an earth (ground) terminal, which must be connected to the ground before
use.
An electrical circuit is usually insulated by an insulating material and encased. However, it is impossible to
manufacture an insulating material that can shut off a leakage current completely, and actually, a slight current flow
into the case. The purpose of earthing (grounding) the case of an electrical apparatus is to prevent operator from
getting an electric shock from this leakage current when touching it.
To avoid the influence of external noises, this earthing (grounding) is important to audio equipment, sensors,
computers and other apparatuses that handle low-level signals or operate very fast.
2) Earthing (grounding) methods and earthing (grounding) work
As described previously, earthing (grounding) is roughly classified into an electrical shock prevention type and a
noise-affected malfunction prevention type. Therefore, these two types should be discriminated clearly, and the
following work must be done to prevent the leakage current having the drive unit's high frequency components from
entering the malfunction prevention type earthing (grounding):
(a)If possible, use (l) independent earthing (grounding) in figure below for the drive unit. If independent earthing
(grounding) is not available, use (ll) joint earthing (grounding) in the figure below where the drive unit is
connected with the other equipment at an earthing (grounding) point. The (lll) common earthing (grounding) as
in the figure below, which drive unit shares a common earthing cable with the other equipment, must be avoided.
A leakage current including many high frequency components flows in the earthing (grounding) cables of the
drive unit and drive unit-driven motor. Therefore, use the independent earthing (grounding) and separate the
earthing (grounding) cable of the drive unit from equipment sensitive to EMI.
In a high building, it may be effective to use the EMI prevention type earthing (grounding) connecting to an iron
structure frame, and electric shock prevention type earthing (grounding) with the independent earthing
(grounding) together.
(b)This drive unit must be earthed (grounded). Earthing (Grounding) must conform to the requirements of national
and local safety regulations and electrical codes. (NEC section 250, IEC 536 class 1 and other applicable
standards).
(c)Use the thickest possible earthing (grounding) cable. The earthing (grounding) cable size should be no less than
the size indicated in the table on the previous page 16.
(d)The grounding point should be as close as possible to the drive unit, and the ground wire length should be as
short as possible.
(e)Run the earthing cable as far away as possible from the I/O wiring of equipment sensitive to noises and run
them in parallel in the minimum distance.
Other
Drive unit
equipment
(I)Independent earthing (grounding).......Best
POINT
To be compliant with the EU Directive (Low Voltage Directive),
(3) Wiring length
Connect a PM motor within the total wiring length of 30m.
Use one dedicated PM motor for one drive unit. Multiple PM motors cannot be connected to a drive unit.
Other
Drive unit
equipment
(II)Common earthing (grounding).......Good
Main circuit terminal specifications
Drive unit
(III)Common earthing (grounding) cable.......Not allowed
refer to the Instruction Manual (Basic).
2
Other
equipment
17